Praise extension filled with aluminium (5)
I believe the answer is:
exalt
'praise' is the definition.
(I know that exalt is a more specific form of praise)
'extension filled with aluminium' is the wordplay.
'extension' becomes 'ext' (abbreviation, as in a telephone extension).
'filled with' indicates putting letters inside.
'aluminium' becomes 'al' (Al is the chemical symbol for aluminium).
'ext' enclosing 'al' is 'EXALT'.
(Other definitions for exalt that I've seen before include "Laud" , "Promote" , "(P) raise" , "delight" , "put on a pedestal" .)